Im undecided if UNO or MEGA, here I can buy the MEGA by 2.3 times the price of an UNO, I have the money for both, but I dont want to know what else offer the Mega to convince myself to expend the money in that, and not another thing.

You didn't state if Mega or Mega2560 but other then memory size those two are equal. You get besides more I/O pins you get 4 hardware serial ports, five user interrupt pins, more timers.

It really depends on the project scope you are going to work with. I still like arduino board that use socketed dip chip 328 processors because you can develop your program on the arduino development board, and then pop the chip out and wire in your project circuit as a standalone microcontroller with just a couple of support components and buy a $6 replacement 328 chip and you are ready to develop your next project. Any of the SMD packaged processors (Uno or mega or nano boards) aren't as DIY friendly for that kind of development cycle.

It also has 8Kb of ram compared to the 2Kb that the Uno as to offer, more timers as said, more ADC inputs, more timers, more hardware pwm's.But the 256k flash is deceiving because gcc can only generate code up to 128Kb.

There's an official Mega, with a 1280 CPU. It has SPI brought out to that double-row connector.

I have no idea whether/how it differs from what Sparkfun sells. I only posted because I remembered reading complaints from people who'd been unpleasantly surprised by the SPI pinout difference, and thought it was worth mentioning to a potential buyer.

On most Arduino boards (those with the ATmega168 or ATmega328), this function works on pins 3, 5, 6, 9, 10, and 11. On the Arduino Mega, it works on pins 2 through 13. Older Arduino boards with an ATmega8 only support analogWrite() on pins 9, 10, and 11. You do not need to call pinMode() to set the pin as an output before calling analogWrite().